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Creating a Console ListBox in C#

Posted by Vulpes Articles | C# Language March 21, 2011
C# developers who are interested in console programming are often frustrated by the lack of user interface features which the console has compared to Windows Forms and WPF applications.
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Introduction

C# developers who are interested in console programming are often frustrated by the lack of user interface features which the console has compared to Windows Forms and WPF applications.

Well, despite the limitations of its text based interface, you can with a bit of effort produce console versions of some of the simpler windows 'controls' and in this article I'd like to show you how to produce a listbox.

To do this we need to draw a box on the console and, fortunately, the unicode character set (as did MS-DOS code pages before it) supports a number of box drawing characters (see http://en.wikipedia.org/wiki/Box-drawing_characters).

Source Code

Here's the source code for producing a basic listbox containing the names of the 12 months of the year:

using System;
 
class ConsoleListBox
{

    static void Main()
    {
        Console.TreatControlCAsInput = false;
        Console.CancelKeyPress += new ConsoleCancelEventHandler(BreakHandler);
        Console.Clear();
        Console.CursorVisible = false;
 
        string[] months = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};

        WriteColorString("Choose Level using down and up arrow keys and press enter", 12, 20, ConsoleColor.Black, ConsoleColor.White);

        int choice = ChooseListBoxItem(months, 34, 3, ConsoleColor.Blue, ConsoleColor.White);
        // do something with choice
        WriteColorString("You chose " + months[choice - 1] + ". Press any key to exit", 21, 22, ConsoleColor.Black, ConsoleColor.White);
        Console.ReadKey();
        CleanUp();
    }

    public static int ChooseListBoxItem(string[] items, int ucol, int urow, ConsoleColor back, ConsoleColor fore)
    {
        int numItems = items.Length;
        int maxLength = items[0].Length;
        for (int i = 1; i < numItems; i++)
        {
            if (items[i].Length > maxLength)
            {
                maxLength = items[i].Length;
            }
        }
        int[] rightSpaces = new int[numItems];
        for (int i = 0; i < numItems; i++)
        {
            rightSpaces[i] = maxLength - items[i].Length + 1;
        }
        int lcol = ucol + maxLength + 3;
        int lrow = urow + numItems + 1;
        DrawBox(ucol, urow, lcol, lrow, back, fore, true);
        WriteColorString(" " + items[0] + new string(' ', rightSpaces[0]), ucol + 1, urow + 1, fore, back);
        for (int i = 2; i <= numItems; i++)
        {
            WriteColorString(items[i - 1], ucol + 2, urow + i, back, fore);
        }

        ConsoleKeyInfo cki;
        char key;
        int choice = 1;
 
        while (true)
        {
            cki = Console.ReadKey(true);
            key = cki.KeyChar;
            if (key == '\r') // enter
            {
                return choice;
            }
            else if (cki.Key == ConsoleKey.DownArrow)
            {
                WriteColorString(" " + items[choice - 1] + new string(' ', rightSpaces[choice - 1]), ucol + 1, urow + choice, back, fore);
                if (choice < numItems)
                {
                    choice++;
                }
                else
                {
                    choice = 1;
                }
                WriteColorString(" " + items[choice - 1] + new string(' ', rightSpaces[choice - 1]), ucol + 1, urow + choice, fore, back);

            }
            else if (cki.Key == ConsoleKey.UpArrow)
            {
                WriteColorString(" " + items[choice - 1] + new string(' ', rightSpaces[choice - 1]), ucol + 1, urow + choice, back, fore);
                if (choice > 1)
                {
                    choice--;
                }
                else
                {
                    choice = numItems;
                }
                WriteColorString(" " + items[choice - 1] + new string(' ', rightSpaces[choice - 1]), ucol + 1, urow + choice, fore, back);
            }
        }
    }

    public static void DrawBox(int ucol, int urow, int lcol, int lrow, ConsoleColor back, ConsoleColor fore, bool fill)
    {
        const char Horizontal = '\u2500';
        const char Vertical = '\u2502';
        const char UpperLeftCorner = '\u250c';
        const char UpperRightCorner = '\u2510';
        const char LowerLeftCorner = '\u2514';
        const char LowerRightCorner = '\u2518';
        string fillLine = fill ? new string(' ', lcol - ucol - 1) : "";
        SetColors(back, fore);
        // draw top edge
        Console.SetCursorPosition(ucol, urow);
        Console.Write(UpperLeftCorner);
        for (int i = ucol + 1; i < lcol; i++)
        {
            Console.Write(Horizontal);
        }
        Console.Write(UpperRightCorner);

        // draw sides
        for (int i = urow + 1; i < lrow; i++)
        {
            Console.SetCursorPosition(ucol, i);
            Console.Write(Vertical);
            if (fill) Console.Write(fillLine);
            Console.SetCursorPosition(lcol, i);
            Console.Write(Vertical);
        }
        // draw bottom edge
        Console.SetCursorPosition(ucol, lrow);
        Console.Write(LowerLeftCorner);
        for (int i = ucol + 1; i < lcol; i++)
        {
            Console.Write(Horizontal);
        }
        Console.Write(LowerRightCorner);
    }

    public static void WriteColorString(string s, int col, int row, ConsoleColor back, ConsoleColor fore)
    {
        SetColors(back, fore);
        // write string
        Console.SetCursorPosition(col, row);
        Console.Write(s);
    }

    public static void SetColors(ConsoleColor back, ConsoleColor fore)
    {
        Console.BackgroundColor = back;
        Console.ForegroundColor = fore;
    }

    public static void CleanUp()
    {
        Console.ResetColor();
        Console.CursorVisible = true;
        Console.Clear();
    }

    private static void BreakHandler(object sender, ConsoleCancelEventArgs args)
    {
        // exit gracefully if Control-C or Control-Break pressed
        CleanUp();
    }
 
}

Output

When you build and run this program, the console should look like this :

List1.gif
 

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